1. Field of the Invention
Arrays of biological tissue can be created by removing cores from regions of interest in a series of donor blocks of embedded tissues. The cores removed are placed in a regular array in a recipient block. This is typically done with two different punches, one for obtaining the cores of interest and the other for creating the receiving holes in the recipient block. The present invention concerns a simplified and economical system and device for creating tissue arrays.
2. Description of the Related Art
Biological tissue arrays consist of regular arrays of cores of embedded biological tissue arranged in a sectionable block typically made of the same embedding material (e.g., paraffin) used originally for the tissue in the cores. The new blocks may be sectioned by traditional means (microtomes etc.) to create multiple nearly identical sections each containing dozens, hundreds or even over a thousand different tissue types. These sections may be used for histochemical and other assays. Any test performed on any one of these sections is effectively performed on hundreds of samples at once. The result is a tremendous saving in effort and time and some increase in the availability and precision of control samples.
Tissue arrays have been constructed entirely manually (Battifora, H., xe2x80x9cThe multitumor (sausage) tissue block: novel method for immunohistochemical antibody testingxe2x80x9d, Laboratory Investigation Vol. 55, pp. 244-248, 1986) and with the assistance of mechanical mechanisms (Kononen et al., xe2x80x9cTissue microarrrays for high-throughput molecular profiling of tumor specimensxe2x80x9d, Nature Medicine Vol. 4, Number 7, pp. 844-847, July 1998) for a variety of biological applications. A manual instrument has also been described in Leighton, U.S. Pat. No. 6,103,518 xe2x80x9cInstrument for constructing tissue arraysxe2x80x9d. Semiautomatic systems have also been proposed (Leighton U.S. patent application Ser. No. 09/811,963 entitled xe2x80x9cDouble Z-Drive Tissue Array Instrumentxe2x80x9d, incorporated herein by reference). The manual methods have largely been superceded by those aided by instruments due to the speed, precision and increased density of the latter. In these devices, two hollow needle-like punches are used, one slightly smaller (recipient punch) than the other (donor punch) to create a hole in a recipient block, typically of paraffin or other embedding medium. The larger or donor punch is used to obtain a core sample from a donor block of embedded biological tissue of interest.
The punches are sized such that the sample obtained just fits in the hole created in the recipient block. Thus the sample is a snug fit in the recipient block and a precise array can be created.
The recipient block is held in an appropriate fixture during the entire processxe2x80x94although it may be removed and alternatingly replaced with one or more other recipient blocks to create more than one array from one set of donor blocks. Micrometer drives or other precision linear positioning means position the punches with respect to the recipient block or the recipient block with respect to the punches. It is clearly desirable that the donor punch reach exactly the same position that the recipient punch reaches on the recipient block for a given setting of the micrometer drives. If it does not, the retrieved sample will not pass smoothly into the hole just created for it, but instead will be damaged or lost. It is further desirable that this motion be created reliably and inexpensively.
In Kononen et al it is taught to use slides and drive mechanisms to first move the recipient punch into a central position and, alternately, the donor punch. This mechanism is cumbersome, expensive, slow and prone to misalignment errors. The use of slides at an intermediate angle such as 45 degrees, as taught by Kononen et al is particularly problematic, as small errors in height positioning can lead to corresponding errors in lateral position and vice versa.
Leighton U.S. Pat. No. 6,103,518 entitled xe2x80x9cInstrument for constructing tissue arraysxe2x80x9d) teaches a turret or other means allowing two punches to share a single z axis slide or drive. This mechanism is appropriate for a simple, manually operated instrument, but may be awkward for an automated instrument in which all motions are driven by powered actuators (pneumatic, electric etc.). Special mechanisms must be machined and assembled, and standard components are not available.
While the above systems are operable, there remains a need for a system which can be fully automated yet has fewer robotic parts than the above-described systems.
It is the purpose of the present invention to allow a standard laboratory robot to be adapted to make tissue arrays. In addition, it is the purpose of the present invention to provide a means for constructing a robust automated instrument.
After extensive investigation, the present inventor realized that in all of the prior art it has been the conventional thinking that the two different punches should be held permanently in some part of the mechanism or drives. Apparently, it may have been thought that permanently holding the punches in respective holders was necessary in order to guarantee accuracy and correct alignment, or that primary goals of operational simplicity and speed in a single, dedicated machine blinded those working in this art to the possibility of using a single set of x-y-z axes and then adding a mechanism for alternately placing first one and then the others of two or more punches into position on the working end of one of the axes.
The present inventor has now surprisingly discovered that the duplex robotics of the prior art are not required, and has developed a simple and precise means of forming tissue arrays by alternately positioning the two different punches in any tissue array instrument.
The invention comprises completely separating the two punches (donor and recipient), giving each their own stylet (unlike Kononen et al) and using a single z-drive (unlike the double z drive disclosed in the Leighton patent application) but not resorting to a cumbersome turret or slider means (as disclosed e.g. in Leighton U.S. Pat. No. 6,103,518 xe2x80x9cInstrument for constructing tissue arraysxe2x80x9d). The improvements over the prior art include using changeable punches that can automatically and alternately be held by a moving gripper and actuator.
The x, y and z drives that are present for general positioning in most laboratory robots can be simply programmed not only to bring the active punch to the appropriate position with respect to a donor or recipient block and to do the punching, but also to bring the punch holder to a magazine or storage area, to release one punch, and to acquire another.
The positions of the tips of the two punches can be periodically measured automatically by sensors mounted on the same pallet as the donor and recipient blocks. Whenever their positions may have moved (perhaps due to encountering a more dense block or irregularity, or perhaps by being disturbed by an operator or foreign object, or simply being altered by virtue of a new punch being installed) then the new positions can be measured and the measurement automatically used to update the offset value. Sensing the tip positions with a sensor mounted on the block holding pallet allows a system to be constructed with standard components and to be robust in the face of environmental challenges and mechanical drift. The position sensing may be used to overcome any variation in tip position caused by alternately replacing the punches automatically.
Typically, the punches are stored in simple holders attached to the same substrate that holds the donor and recipient blocks and a complementary holder or gripping means is attached to a member or arm that can move in x, y and z with respect to said substrate. (Of course, there are various combinations of motion that are obvious to one skilled in the art, such as having the substrate fixed with respect to the laboratory frame of reference and the arm moving in x, y and z or the substrate moving in x an y and the arm moving only in z or the substrate moving in x and the arm moving in y and z etc. The reference to movement in the z axis should be understood as relative movement between punch and donor or recipient block.) The holder or gripping means can be switched between a gripping and releasing mode by the same computer or controller that is controlling the rest of the operations of the instrument, or the gripping and releasing may be entirely mechanical, activated by the approach and withdrawal motions of the gripper with respect to the holding location.
Once the appropriate punch is firmly held in the gripping means, the motion drive can move the punch to the appropriate position for punching holes in a recipient block, discharging waste to a waste receptacle, acquiring tissue from a donor block, or inserting tissue into a recipient block. A surface sensing device could either be permanently attached to the moving arm or could be an alternate tool that can be picked up when needed instead of one of the punches.
Since each of the two punches can be picked up and used by the same axis, only one x, y, z drive system is required. Compare Kononen et al, where six drives are required, two for moving the two punches into and out of position, one for moving the punches into and out of the blocks and two for x, y motions of the blocks. In Leighton (U.S. Pat. No. 6,103,518 xe2x80x9cInstrument for constructing tissue arraysxe2x80x9d), manual operation is contemplated, but were the system to be automated, four drives would be required, and they would need to be of two different types, one for toggling the turret from one position to the other, and another for moving the turret up and down. This would result in greater costs, as two different types of drives would be required to be designed and manufactured for the two different types of motion.
In the present invention, a standard laboratory robot can be used, leading to reduced costs and simplicity.
While two punches are employed in the above discussion for simplicity, it will be readily understood that it is easily within the scope of this invention to use more than two punches, each stored in a similar holder on the substrate, for example to permit quick changes between different sizes of punches for different applications. It is also possible to use the punch holder to hold a tool for moving blocks, a tool for labeling blocks, or other tools or devices.
The rest of the system may be similar to that already described in the prior art. For example, powered or manual micrometer drives or the like may be used to position the punching mechanism over the blocks or the blocks under the punching mechanism. A removable bridge may be used for supporting the donor blocks over the recipient blocks, or the donor blocks may be attached to the same pallet that holds the recipient blocks. The latter arrangement allows the same x and y drives and slides to be used for both donor and recipient blocks. Alternately, separate x, y systems could be used for the recipient blocks and the donor blocks. This is more complicated, but can permit faster operation for high-throughput systems.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description of the invention that follows may be better understood, and so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other tissue arrayers for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent structures do not depart from the spirit and scope of the invention as set forth in the appended claims.